1. Field of the Invention
The present invention relates to feeding of a recording medium in printers. More specifically, the present invention relates to controlling the timing for feeding a next sheet of a recording medium based on a calculation of an expected detection of an end of a current sheet so that feeding of the next sheet is initiated prior to detection of the end of the current sheet.
2. Description of the Related Art
Printers print images onto a sheet of paper that is fed through the printer by a series of rollers that are actuated by one or more motors. Generally, paper feeding is performed by the following components: a paper tray, an automatic sheet feed (ASF) roller, a line feed (LF) roller, an ASF motor for actuating the ASF roller, a LF motor for actuating the LF roller, a page edge (PE) sensor, and a controller. Each of these components operate in conjunction with one another to feed a sheet of paper from the paper tray through the printer.
Generally, when printing is to commence, the controller sends a signal to the ASF motor to actuate and to begin turning the ASF roller. The ASF roller rotates to pick up a sheet of paper from the paper tray and feeds it into the printer so that a leading edge of the paper engages a registration position. The registration position provides for a known starting point for paper feeding during printing and is located in a proximity to the LF roller. As the paper is fed into the printer by the ASF roller, the PE sensor senses when the leading edge of the paper has been encountered and sends a signal to the controller, thereby confirming that the paper has been fed into the printer.
After the paper has been fed into the printer to the registration position, the controller stops the ASF motor and sends a signal to the LF motor to start turning. The LF motor engages the LF roller which rotates to pick up the leading edge of the paper and to feed it through the printer while a recording head prints an image onto the paper. When the image has been printed, the controller signals the LF motor to rotate to eject the paper from the printer. As the paper is being ejected from the printer, the PE sensor senses the trailing edge of the paper and sends a signal to the controller. When the controller receives the signal from the PE sensor indicating that the end of the sheet has been detected, the controller starts the process over for the next sheet.
Thus, when printing multi-page print jobs, conventional printers do not begin feeding the next sheet until the end of the current sheet has been detected. Waiting to detect the end of the current sheet before starting to feed the next sheet means that more time is required for processing the print job. For instance, if it takes one second from the time the end of the current sheet is detected until the next sheet begins to be fed, then the total processing time for a 60 page print job would be increased by one minute due to the page feeding operations. Therefore, one way to reduce the processing time for printing multi-page print jobs would be to reduce the time for loading a next sheet during printing.
One way to address the foregoing could be to locate the mechanical components closer to each other so that the paper does not have to travel as far during the feeding operation. However, this solution would not be practical for existing printers since it would require costly structural and mechanical changes. Moreover, physical constraints may limit the proximity that the components can be located relative to each other.
Another way to address the foregoing may be to provide a faster ASF motor. However, such a motor may be more costly than existing motors and may also require complex and costly hardware changes to existing printers.
Therefore, what is needed is a way to reduce printing time by reducing the time required for feeding successive sheets of paper without requiring costly hardware changes.
The present invention addresses the foregoing by initiating feeding of a next sheet prior to detection of the end of a current sheet. Initiating feeding of a next sheet without waiting for the end of the current sheet to be detected reduces the time required for printing multi-page print jobs since the time required for feeding is reduced.
According to one aspect, the invention may be feeding a plurality of successive sheets of a recording medium into a printer by calculating an expected time when a page end detection of a current sheet of the successive sheets is expected, and feeding a next sheet of the successive sheets in accordance with the calculated time, but prior to detection of the page end of the current sheet.
As a result of the foregoing, successive sheets are fed into the printer faster than conventional printers since the next sheet begins being fed into the printer without waiting for the end of the current sheet to be detected. Therefore, the time required for printing multi-page print jobs is reduced since the time required for feeding the paper is reduced. Additionally, the invention can be implemented in existing printers as software or firmware without the need for costly and possibly impracticable hardware changes.
In calculating the expected time, the invention may provide for detecting the page end for the current sheet, and mathematically filtering the page end detection of the current sheet with a current estimate of expected time for page end detection of the next sheet so as to update the estimate throughout processing of the successive sheets. The current estimate may be initialized after a first sheet of the successive sheets with a page end detection of the first sheet.
Additionally, the feeding of the next sheet may be controlled by controlling a time between the current sheet and the next sheet based on a time between the page end detection of the current sheet and a detection of the next sheet. The time between the current sheet and the next sheet may be controlled to obtain and maintain the time within a target range.
Controlling the time for feeding the sheets based on the time between the page end detection of the current sheet and detection of the next sheet provides for a reduction in the distance between each successive sheet until a target distance is obtained. As a result, a more optimum spacing can be achieved, thereby reducing the processing time even more.
In related aspects, the invention may provide for determining whether the end of the current sheet is detected within a threshold amount of time after feeding of the next sheet has commenced, and, in a case where it is determined that the end of the current sheet is not detected within the threshold, feeding of the next sheet is interrupted and a recovery process is engaged. The recovery process may be waiting to detect the end of the current sheet and re-initiating feeding of the next sheet.
These further aspects provide additional ways for the printer to optimize the spacing between sheets being fed into the printer. This is accomplished by detecting whether the end of the current sheet has cleared the edge detector prior to the next sheet""s leading edge approaching the detector. This helps to optimize the distance between sheets and reduces the possibility of a paper jam.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings.